Production of acetylene by incomplete combustion of hydrocarbons with oxygen



y 6, 1958 E. LEHRER ,833,839

pnonuc'rron 0F ACEI'YLENRBY mcowwrs cowausnow OF HYDROCARBONS WITH OXYGEN Filed Feb. 21. 1955 PREHEATED IRWIN LEHRER ATT'YS United rates Patent PRODUCTION OF ACETYLENE BY INCOMPLETE gglgglBUSTION 0F HYDROCARBONS WITH GEN Lehrer, Bad Duerkheim, Germany, assiguor to Badische Anilin- & Soda-Fabrik Aktiengesellschaft, Ludwigshafen (Rhine), Germany Application February 21', 1955, Serial No. 489,807

Claims priority, application Germany March 11, 1954 4 Claims. (Cl. 2'60 -679) This invention relates to improvements in the production of acetylene by incomplete combustion of hydrocarbons.

Processes for the production of acetylene by incomplete combustion of gaseous or vaporous hydrocarbons with oxygen are already known in which the hydrocarbons and the oxygen are separately preheated, then mixed and after the most complete mixing possible are subjected to a flame reaction. An elongated arrangement of circular cross-section, such as is described in the patent specification No. 2,664,450, is especially suitable as a mixing apparatus. The hydrocarbon and the oxygen enter this apparatus at high speed. The final mixture leaves the mixing chamber through a number of parallel channels and flows into the reaction chamber in which its components react with each other with the formation of a flame. The reaction gas is cooled as rapidly as possible. preferably by spraying in water.

In carrying out this process it has been observed that the hot mixture of hydrocarbon and oxygen occasionally ignites in the mixing chamber, so that it is possible for a stationary flame to form, in particular at the point at which the hydrocarbon and the oxygen meet. By reason of the high temperature of this flame, the mixing chamber and the associated channels are destroyed in a short time if the flow of oxygen is not promptly turned oft". This, however, leads to undesirable interruptions of the operation.

Attempts have been made to prevent the formation of a stationary flame in the mixing chamber by allowing the two gases to flow together through concentric tubes, preferably in the same direction, the sum of their mean speeds being greater than 70 metres per second, measured at 0 C. and 760 mm. of Hg. For example the speed of methane was about 150 to 200 metres per second and that of the oxygen about 300 metres per second, measured under operational conditions. It has been found however that with large throughputs of considerably more than 1000 normal cubic metres per hour of hydrocarbon and at preheating temperatures above 500 C. these measures are not suflicient to avoid with certainty the formation of a stationary flame and consequently an interruption of the operation or injury to the apparatus.

According to the present invention the formation of a stationary flame is prevented even when employing throughputs of more than 1000 normal cubic metres per hour and preheating temperatures above 500 C., by maintaining the highest possible speeds of hydrocarbon and oxygen and choosing the speed of the hydrocarbon greater than that of the oxygen. In the abovementioned example, therefore, the speed of the hydrocarbon should amount to more than 300 metres instead of only 150 to 200 metres per second.

Especially favorable results or obtained when the ratio of the speed of the hydrocarbon to that of the oxygen lies between the ratio of the density of oxygen to that of the hydrocarbon and the square root of this ratio. If

2,833,839 Patented May 6, 1958 2 ignition occurs in the mixing chamber it does not lead to a stationary flame. On the contrary the flame formed for a short time is carried out from the mixing chamber by the flowing gas and therefore cannot cause damage in the heated gases to be reacted are supplied at high speed through a pair of concentric tubes 2. and 3. The oxygen supplied through tube 2 and the gaseous or vaporous hydrocarbon supplied through tube 3 meet at high speed at the inlet end 4 of the chamber 1 and form a gaseous or vaporous mixture which passes out of the chamber 1 through parallelchannel-s 5 into a reaction chamber 6 in which the mixture is reacted with an accompanying flame to form the acetylene.

The following example will further illustrate this invention but the invention is not restricted to this example.

Example 1800 normal cubic metres per hour of methane are heated to 600 C. in a preheater and 1050 normal-cubic metres per'hour of oxygen are also; heated to a temperature of 600 C. in a second preheater. The hot gases are supplied to the mixing apparatus claimed in the United States Patent 2,664,450. After complete mixing, the mixture enters through the parallel channels into the reaction chamber where the methane reacts with the oxygen with the formation of a flame. The reaction gases are rapidly cooled by spraying in water. There are thus formed 3400 normal cubic metres per hour of a gas mixture which contains about 8.5% of acetylene.

The cross-sections of the mixing apparatus are chosen so that at the point of mixing the methane has a speed of 500 metres per second, measured at 600 C. and 1 atmosphere (absolute) and the oxygen has a speed of 300 metres per second under the same conditions. The ratio of the speed of the methane to that of the oxygen is 1.67 and thus lies between the ratio of the density of oxygen to the density of methane (l.43:0.715=2) and the square root of theratio of these densities /E=1.4l).

If under these conditions a flame forms in the mixing chamber, it is in every case carried out from the mixing chamber by the flow. With this arrangement, not a single operational interruption by reason of the formation of a stationary flame occurs in a period of operation of several weeks.

If, however, the total throughput is reduced to less than half, so that the speed of the oxygen is less than metres per second, or if the cross-section of the mixing apparatus is changed so that the speed of one or both of the gases is less'than 150 metres per second while retaining the original throughput, ignitions in the mixing chamber lead to operational interruptions by reason of the formation of a stationary flame.

I claim:

1. In a process for the production of acetylene by incomplete combustion of a preheated hydrocarbon gas with preheated oxygen wherein the two preheated gases are supplied separately through concentric tubes into an elongated mixing chamber of circular cross-section, the two gases are mixed in said mixing chamber and distributed therefrom by means of a plurality of parallel channels into a combustion chamber in which said gases react with flame formation, and the gaseous reaction products are rapidly cooled by spraying with water, the improvement for avoiding formation of a stationary flame in said mixing chamber which comprises: maintaining the mean speed of flow of the two gases at their junction point in the mixing chamber at not less than 150 meters carbon gas being greater than that of the preheated oxygen at said junction point, at a hydrocarbon gas throughput of more than 1000 normal cubic meters per hour and preheating temperatures above 500 C.

2. A process as defined in claim 1 wherein the speed of flow of the preheated oxygen at the junction point is at least 300 meters per second.

3. In a process for the production of acetylene by incomplete combustion of a preheated hydrocarbon gas with preheated oxygen wherein the two preheated gases are supplied separately through concentric tubes into an elongated mixing chamber of circular cross-section, the two gases are mixed in said mixing chamber and distributed therefrom by means of a plurality of parallel channels into a combustion chamber in which said gases react with flame formation, and the gaseous reaction products are rapidly cooled by spraying with water, the improvement for avoiding formation of a stationary flame in said mixing chamber which comprises: maintaining the mean speed of flow of the two gases at their junction point in the mixing chamber at not less than 150 meters per second, the ratio of the speed of flow of the hydro carbon to the speed of flow of the oxygen being in a range between the ratio of the density of oxygen to the density of the hydrocarbon and the square root of said density ratio, at a hydrocarbon gas throughput of more than 1000 normal cubic meters per hour and preheating temperatures above 500 C.

4. In a process for the production of acetylene by incomplete combustion of preheated methane with preheated oxygen wherein the two preheated gases are supplied separately through concentric tubes into an elongated mixing chamber of circular cross-section, the two gases are mixed in said mixing chamber and distributed therefrom by means of a plurality of channels into a combustion chamber in which said gases react with flame formation, and the gaseous reaction products are rapidly cooled by spraying with water, the improvement for avoiding formation of a stationary flame in said mixing chamber which comprises: maintaining the mean speed of flow of the preheated methane and oxygen gases at their junction point in the mixing chamber at not less than meters per second, the ratio of the speed of flow of methane to the speed of flow of oxygen at said junction point being in a range of from 1.41:1 to 2:1, at a methane throughput of more than 1000 normal cubic meters per hour and preheating temperatures above 500 C.

References Cited in the file of this patent UNITED STATES PATENTS 1,823,503 Mittasch et a1 Sept. 15, 1931 1,965,771 Groll et al July 10, 1934 2,520,149 Keeling Aug. 29, 1950 2,572,664 Robinson Oct. 23, 1951 2,664,450 Sachsse et a1 Dec. 29, 1953 2,722,553 Mullen et al Nov. 1, 1955 FOREIGN PATENTS 709,035 Great Britain May 12, 1954 

1. IN A PROCESS FOR THE PRODUCTION OF ACETYLENE BY INCOMPLETE COMBUSTION OF A PREHEATED HYDROCARBON GAS WITH PREHEATED OXYGEN WHEREIN THE TWO PREHEATED GASES ARE SUPPLIED SEPARATELY THROUGH CONCENTRIC TUBES INTO THE ELONGATED MIXING CHAMBER OF CIRCULAR CROSS-SECTION, THE TWO GASES ARE MIXED IN SAID MIXING CHAMBER ANS DISTRIBUTED THEREFORM BY MEANS OF A PLURALITY OF PARALLEL CHANNELS INTO A COMBUSTION CHAMBER IN WHICH SAID GASES REACT WITH FLAME FORMATION, AND THE GASEOUS REACTION PRODUCTS ARE RAPIDLY COOLED BY SPRAYING WITH WATER, THE IMPROVEMENT FOR AVOIDING FORMATION OF A STATIONERY FLAME IN SAID MIXING CHAMBER WHICH COMPRISES: MAINTAINING THE MEANS SPEED OF FLOW OF THE TWO GASES AT THEIR JUNCTION POINT IN THE MIXING CHAMBER AT NOT LESS THAN 150 METERS PER SECOND, THE SPEED OF FLOW OF THE PREHEATED HYDROCARBON GAS BEING GREATER THAN THAT OF THE PREHEATED OXYGEN AT SAID JUNCTION POINT, AT A HYDROCARBON GAS THROUGHPUT OF MORE THAN 1000 NORMAL CUBIC METERS PER HOUR AND PREHEATING TEMPERATURES ABOVE 500*C. 